import java.util.List;

public class MySingleList {

    static class ListNode{
        public int val;//节点的值域
        public ListNode next;//下个节点的地址
        public ListNode(int val){
            this.val = val;
        }
    }
    public ListNode head;//表示当前链表的头节点

    public void creatList(){
        ListNode node1 = new ListNode(12);
        ListNode node2 = new ListNode(23);
        ListNode node3 = new ListNode(34);
        ListNode node4 = new ListNode(45);
        ListNode node5 = new ListNode(56);

        node1.next = node2;
        node2.next = node3;
        node3.next = node4;
        node4.next = node5;

        this.head = node1;
    }
    public void display(){
        ListNode cur = head;
        while(cur != null){
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }

    public int size(){
        int count = 0;
        ListNode cur = head;
        while (cur != null){
            count++;
            cur = cur.next;
        }
        return count;
    }

    public boolean contains(int key){
        ListNode cur = head;
        while (cur != null){
            if(cur.val == key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    public void addFirst(int data){
        ListNode node = new ListNode(data);
        node.next = head;
        head = node;
    }
}
